Changes

The second method is to use [https://en.wikipedia.org/wiki/Quaternion quaternions]. Any arbitrary rotation can be entirely done about a unique axis and using a particular rotation angle about it. So we have four parameters in a quaternion; three to give this axis as a vector (vector part) and one for the rotation angle(scalar part). These four are intertwined in the sense that the vector part doesn’t give you the axis alone.<br \>

There is an interesting story about Hamilton who had devised quaternions. So Hamilton was on his way to preside a meeting when the idea of quaternions dawned upon him. He had been struggling to extrapolate the idea of 2-D rotation which can be done using complex numbers to 3-D. And when he had his moment of epiphany, he got so excited that he couldn’t resist the urge to carve its formulae into the stone of Brougham Bridge as he paused on it. <br \>